This invention relates to fluid flow control devices, and more particularly, to such a device which limits draining of fluid back through the device.
In various applications of irrigation systems, it has been found quite advantageous to provide a device which insures a substantially constant water flow therethrough, even though the pressure of the water being delivered to the device may vary. Devices for providing such operation are generally disclosed in U.S. Pat. No. 2,389,134 to Brown, and U.S. Pat. No. 2,454,929 to Kempton. Such a device may be used with particular advantage in the lowest-positioned sprinkler of an irrigation system including a number of sprinklers. This is so because the pressure head applied to this lowermost sprinkler results in increased flow-inducing pressure being applied to such lowermost sprinkler, as compared to the sprinklers elevationally above it.
While such systems are quite advantageous in use, it will be understood that, when they are used in accordance with the teaching of such patents and in combination with, for example, a sprinkler irrigation system, certain problems exist. For example, when a system incorporating such devices is shut off, such devices allow water to drain off from such sprinkler nozzle at the lowest elevation of the system. If in fact the sprinkler is lower than the rest of the system, eventually all of the water will drain from the system. Such drainage is a serious problem in that the draining water causes erosion of the soil and damage to crops. Additionally, if the sprinkler system completely drains, aluminum tubing in the system is subject to a greater expansion and contraction from temperature differences than would be the case if such tubing was filled with water. It has been found that with empty aluminum tubing, the expansion and contraction may be enough to cause couplers connecting portions of the tubing to become unlatched. Furthermore, on many large systems, it is quite expensive to continually refill the drained system with water.